The present invention pertains to closed plastic containers and, more particularly, to containers having a separate cup and lid which, when attached to close the container, provide a continuous seal and locked engagement.
Plastic containers are widely used for innumerable packaging functions. Flexible thin wall plastic containers are particularly attractive in food service and similar applications because of their light weight and low cost. Such containers are commonly made using thermoforming or vacuum forming techniques. There are many plastic resins which are suitable for these containers, including PET and polystyrenes.
When used as beverage containers or containers for other liquid food products, the cups are typically closed with a generally flat lid that snaps over the lip defining the mouth of the cup. The lid may be completely closed to prevent or inhibit leakage or may have openings or openable areas for access, as for a drinking straw. Snap-on lids or covers, though providing some protection against leakage and spillage, are not secure. These lids are quite easily inadvertently dislodged by the user and cannot provide a secure closure if the container is tipped over, much less so if it is dropped.
It would be desirable to have a container, such as a beverage cup and lid, in which the lid could be readily attached in a manner that provides a liquid-tight seal and also lock the lid against inadvertent opening. It would be desirable to have such a sealing and locking cup and lid in which the lid could be readily removed by the user if desired.
In accordance with the present invention, a sealed, locked and reopenable cup and lid assembly utilizes a cup that has an open circular mouth defined by an upper edge, an inwardly opening locking groove below the upper edge, and a frustoconical inner wall portion that extends downwardly and diverges outwardly from the locking groove; a resilient circular lid that is sized to be inserted into the open mouth of the cup and has an outer peripheral lip that is received with a snap fit in the locking groove in the cup, and a frustoconical sealing wall that extends downwardly and diverges outwardly from the peripheral lip and sealingly engages the frustoconical inner wall portion on the cup; and, interrupted portions in the locking groove and in the peripheral lip that are circumferentially spaced and rotationally alignable to permit removal of the lid.
Preferably, the locking groove is defined by a plurality of protrusions that extend radially inwardly from the upper edge of the cup and an annular horizontal cup wall portion positioned below and spaced from the protrusions. The outer peripheral lip of the lid preferably comprises generally horizontal upper and lower lip surfaces that are interconnected by a generally vertical intermediate lip surface. The protrusions have generally coplanar lower surfaces and the peripheral lip is captured in the locking groove by engagement of the upper and lower surfaces of the lip with the lower surfaces of the protrusions and the horizontal wall portion, respectively. The interrupted portions in the peripheral lip of the lid are in the form of recesses that correspond to the protrusions on the upper edge of the cup and permit reopening movement of the lid past the protrusions.
The frustoconical inner wall portion of the cup extends downwardly from the radially inner edge of the horizontal wall portion and forms with it an edge bead having a first diameter. The frustoconical sealing wall on the lid extends downwardly from the radially inner edge of the lower lip surface and forms with it a second edge bead having a second diameter greater than the first diameter. The second edge bead is adapted to override the first edge bead by lateral deflection in response to lid insertion and to resiliently return to provide the sealing engagement between the frustoconical sealing wall of the lid and the frustoconical wall portion of the cup. Preferably, the angle of divergence of the frustoconical wall portion is less than the angle of divergence of the frustoconical sealing wall.